Although much important biological research has been conducted on Bipolar disorder, little methodologically rigorous or theory guided work has examined psychosocial factors in the onset and course of this disorder. Moreover, although individuals exhibiting Cyclothymia, a subsyndromal form of bipolar disorder, are at high risk for developing full blown syndromal bipolar I or II disorder, little is known about: 1) the predictors of which cyclothymic individuals eventually do develop syndromal Bipolar disorder and which do not; or 2) the mechanisms involved in the development of syndromal Bipolar disorders among cyclothymics. Thus, the overarching goal of this proposal is to provide a theoretically consistent and methodologically rigorous examination of life events, cognitive processes, and personality factors in the course of Cyclothymia and initial onset and course of full blown syndromal Bipolar disorder among cyclothymics. The application of the cognitive diathesis-stress theories (Beck's theory and the Hopelessness theory), which have been so useful for unipolar depression, will be examined for cyclothymia and Bipolar disorder. To this end, a large scale, 3-year prospective study designed to examine life events, cognition, and personality factors in the course of cyclothymia and initial onset and course of Bipolar I or II disorder will be conducted. Three hundred Cyclothymics with not lifetime history of major depressive or full syndromal manic episodes and 300 demographically- matched normal controls with not lifetime history or any psychopathology will be followed prospectively with independent and blind self-report and interview assessments (every 16 weeks) of life events, cognition, and psychiatric status/symptoms in order to predict onset, course, and subsequent relapses/recurrences of syndromal and subsyndromal depression and mania. This study will contribute to: 1) knowledge about psychosocial factors in the course of Cyclothymia and initial onset and subsequent course of full blown bipolar disorder; 2) elucidation of the relationship between unipolar and bipolar depression; 3) development of interventions for treating and preventing bipolar disorder.